Five year results of US intergroup/RTOG 9704 with postoperative CA 19-9 ≤90 U/mL and comparison to the CONKO-001 trial

Purpose: Radiation Therapy Oncology Group (RTOG) trial 9704 was the largest randomized trial to use adjuvant chemoradiation therapy for patients with pancreatic cancer. This report analyzes 5-year survival by serum level of tumor marker CA 19-9 of ≤90 vs >90 U/mL and compares results to the those of the CONKO-001 trial. Methods and Materials: CA 19-9 expression was analyzed as a dichotomized variable (≤90 vs >90 U/mL). Cox proportional hazard models were used to identify the impact of the CA 19-9 value on overall survival (OS). Actuarial estimates of OS were calculated using the Kaplan-Meier method. Results: Both univariate (hazard ratio [HR] = 3.2; 95% confidence interval [CI], 2.3-4.3, P<.0001) and multivariate (HR = 3.1; 95% CI, 2.2-4.2, P<.0001) analyses demonstrated a statistically significant decrease in OS for CA 19-9 serum level of ≥90 U/mL. For patients in the gemcitabine (Gem) treatment arm with CA 19-9 <90 U/mL, median survival was 21 months. For patients with CA 19-9 ≥90 U/mL, this number dropped to 10 months. In patients with pancreatic head tumors in the Gem treatment arm with RT quality assurance per protocol and CA 19-9 of <90 U/mL, median survival and 5-year rate were 24 months and 34%. In comparison, the median survival and 5-year OS rate for patients in the Gem arm of the CONKO trial were 22 months and 21%. Conclusions: This analysis demonstrates that patients with postresection CA 19-9 values ≥90 U/mL had a significantly worse survival. Patients with pancreatic head tumors treated with Gem with CA 19-9 serum level of <90 U/mL and per protocol RT had favorable survival compared to that seen in the CONKO trial. CA 19-9 is a stratification factor for the current RTOG adjuvant pancreas trial (0848).